On 5/27/15, 9:01 AM, Scott Feldman wrote:
On Wed, May 27, 2015 at 1:35 AM, Nikolay Aleksandrov
<nikolay@xxxxxxxxxxxxxxxxxxx> wrote:
On Wed, May 27, 2015 at 9:59 AM, Scott Feldman <sfeldma@xxxxxxxxx> wrote:
On Wed, May 27, 2015 at 12:05 AM, Nikolay Aleksandrov
<nikolay@xxxxxxxxxxxxxxxxxxx> wrote:
On Tue, May 26, 2015 at 7:28 PM, Stephen Hemminger
<stephen@xxxxxxxxxxxxxxxxxx> wrote:
On Thu, 21 May 2015 03:42:57 -0700
Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx> wrote:
From: Wilson Kok <wkok@xxxxxxxxxxxxxxxxxxx>
Check in fdb_add_entry() if the source port should learn, similar
check is used in br_fdb_update.
Note that new fdb entries which are added manually or
as local ones are still permitted.
This patch has been tested by running traffic via a bridge port and
switching the port's state, also by manually adding/removing entries
from the bridge's fdb.
Signed-off-by: Wilson Kok <wkok@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
What is the problem this is trying to solve?
I think user should be allowed to manually add any entry
even if learning.
Hi Stephen,
I have been thinking about the use case and have discussed it
internally with colleagues and the patch
author, the main problem is when there's an external software that
adds dynamic entries (learning) and
it could experience a race condition, here's a possible situation:
* external software learns a mac from hw, sends an add to kernel
* right before that, port goes blocking (or down) and kernel flushes
mac, sends notification about the state change and mac flush
* right after that, kernel gets the previous add from external software, it's
allowed to add, and then sends an add notification
* mean while, external software processes the link block/down and mac flush,
followed by the mac add from kernel. At this point, external software can't
really know whether it's a user adding the mac intentionally or it's
a race.
This issue can't really be avoided in user-space.
As I've noted local and static entries are still allowed, and iproute2
bridge utility always
marks the entries as static (NUD_NOARP), this only affects external
dynamic entries which
are usually sent by something that does the learning externally.
I'll keep digging to see if there's another way to go about this since
I'd like to give the user
full freedom. Personally I don't have strong feeling for this patch
and if it's not preferred then
I'll post a revert.
So there is already a switchdev API to add/del an externally learned
FDB entry which holds rtnl_lock and avoids these races. I would
suggest using that and revert this patch.
See call_switchdev_notifiers(SWITCHDEV_FDB_ADD|SWITCHDEV_FDB_DEL) and
the handler in br.c:br_switchdev_event().
-scott
Hmm, I'm new to the switchdev API and am possibly missing something,
but how do you suggest to use it here ?
You need to call
call_switchdev_notifiers(SWITCHDEV_FDB_ADD|SWITCHDEV_FDB_DEL) when the
device learns a new mac/vlan on the port interface.
How can we differentiate between user-added entry and an externally
learned one ?
Externally added ones will be marked with NTF_EXT_LEARNED set in
ndm->ndm_flags in the netlink echo. Manually added ones from the user
will have ndm->ndm_state set to NUD_NOARP in the netlink echo.
Do you mean to use (for example) the NTF_EXT_LEARNED flag when adding
an entry from user-space so
the API can get called in br_fdb_add ?
No. br_fdb_add is the bridge's .ndo_fdb_add handler called when user
manually adds an FDB entry using netlink RTM_NEWNEIGH. For externally
learned entries, use the internal
call_switchdev_notifiers(SWITCHDEV_FDB_ADD|SWITCHDEV_FDB_DEL).
scott, I am assuming you are ok with an external learning entity (user
space driver or a controller) pushing entries
with the NTF_EXT_LEARNED correct ?. Because NTF_EXT_LEARNED is in uapi
(and analogous to RTNH_F_OFFLOAD in the fib offload world IMO)
